Functional fluids

ABSTRACT

FUNCTIONA FLUIDS COMPRISING A MAJOR AMOUNT OF A PHOSPHORAMIDATE AND A MINOR AMOUNT OF A MIXTURE OF (1) A NITROGEN-CONTAINING ANTIOXIDANT AND (2) A NITROGEN-CONTAINING HETEROCYCLIC COMPOUND HAVE GREATLY REDUCED CORROSIVENESS TO METAL MECHANICAL MEMBERS IN CONTACT WITH SAID FLUIDS. THE FLUID COMPOSITIONS ARE USEFUL AS HYDRAULIC FLUIDS, DAMPING FLUIDS, HEAT TRANSFER FLUIDS AND THE LIKE.

United States Patent 3,778,376 FUNCTIONAL FLUIDS John F. Herber, St. Louis, Mo., assignor to Monsanto Company, St. Louis, M0.

N0 Drawing. Continuation-impart of abandoned application Ser. No. 562,520, July 5, 1966. This application Dec. 8, 1969, Ser. No. 883,341

Int. Cl. C091: 3/00 US. Cl. 252-78 3 Claims ABSTRACT OF THE DISCLOSURE Functional fluids comprising a major amount of a phosphoramidate and a minor amount of a mixture of (1) a nitrogen-containing antioxidant and (2) a nitrogen-containing heterocyclic compound have greatly reduced corrosiveness to metal mechanical members in contact with said fluids. The fluid compositions are useful as hydraulic fluids, damping fluids, heat transfer fluids and the like.

This application is a continuation in part of application Ser. No. 562,520, filed July 5, 1966 and now abandoned.

This invention relates to certain new functional fluid compositions comprising a phosphoroamidate base stock, a nitrogen-containing antioxidant and a nitrogen-containing heterocyclic compound, which new functional fluid compositions have the ability to inhibit and control corrosion damage to mechanical members in contact with said compositions.

Many different types of materials are utilized as functional fluids and functional fluids are used in many different types of applications. Such fluids have been used as electronic coolants, atomic reactor coolants, diffusion pump fluids, synthetic lubricants, damping fluids, bases for greases, force transmission fluids (hydraulic fluids), heat transfer fluids, die casting release agents in metal extrusion processes and as filter mediums for air conditioning systems. Because of the wide variety of applications and the varied conditions under which functional fluids are utilized, the properties desired in a good functional fluid necessarily vary with the particular application in which it is to be utilized with each individual application requiring a functional fluid having a specific class of properties.

Of the foregoing the use of functional fluids as heat transfer fluids and hydraulic fluids, particularly aircraft hydraulic fluids, has posed what are probably the most diflicult areas of application. Thus, the requirements of a heat transfer fluid are as follows: The fluid should be liquid over a Wide temperature range, and in general have a low vapor pressure so as to be utilized at atmospheric pressure. Such fluid should be operable as a heat transfer media over an extended period of time at given temperatures and should in addition be non-flammable, nontoxic and exhibit a high degree of thermal and hydrolytic stability.

The requirements for an aircraft hydraulic fluid can be described as follows: The hydraulic power systems of aircraft for operating various mechanisms of an airplane impose stringent requirements on the hydraulic fluid used. Not only must the hydraulic fluid for aircraft meet stringent functional and use requirements but in addition such fluid should be as non-flammable as possible and must have suflicient fire-resistance to satisfy aircraft requirements. The viscosity characteristics of the fluid must be such that it may be used over a wide temperature range; that is, adequately high viscosity at high temperature, low viscosity at low temperature and a low rate of change of viscosity with temperature. Such temperature range is generally from 40 F. to 450 F. Its pour point should be low. Its volatility should be low at elevated temperatures of use and the volatility should be balanced; that is, selective evaporation or volatilization of any important component should not take place at the high temperatures of use. It must possess suflicient lubricity and mechanical stability to enable it to be used in the self-lubricated pumps, valves, etc., employed in the hydraulic systems of aircraft which are exceedingly severe on the fluid used. It should be thermally and chemically stable in order to resist oxidation and decomposition so that it will remain uniform under conditions of use and be able to resist the loss of desired characteristics due'to high and sudden changes of pressure and temperature, high shearing stresses, and contact with various metals which may be, for example, aluminum, bronze, copper and steel. It should also not deteriorate the gaskets or packings of the hydraulic system, and in the event of a leak, should not adversely affect the various parts of the airplane with which it may accidentally come in contact, such as electrical wire insulation and paint. It should not be toxic or harmful to personnel who may come in contact with it.

A particular problem associated with the use of a functional fluid in the many applications described above is the tendency of metal mechanical members in contact with the functional fluid to corrode, including members made of metals such as aluminum, bronze, copper, steel and various alloys which utilize many types of metals in the alloy composition. Corrosion of mechanical members in contact with a functional fluid adversely alfects not only the mechanical members, however, but also the functional fluid itself. Corrosion damage to mechanical members in contact with a functional fluid can cause alteration of the geometry of the mechanical members in contact with the fluid, and in addition corrosion products can precipitate as well as being solubilized into the functional fluid. As a consequence of the corrosion of mechanical members, the close tolerances which are required for certain mechanical members are altered and excessive wear results. The excessive rate of wear necessitates premature removal of mechanical parts, filter plugging and excessive replacement of filters, and in addition fluid contamination. As discussed above, mechanical members are adversely affected when corrosion occurs and one of the results of corrosion is the formation of corrosion products which cause fluid contamination. Also, the corrosion products are believed to be metal salts which can act as pro-oxidants and increase the rate of oxidation of a functional fluid. Thus, the presence of such corrosion products causes fluid degradation which degradation manifests itself in numerous ways, among which are viscosity change, increase in acid number, formation of insoluble materials as a result of the oxidation of the base stock, increase in chemical reactivity and discoloration. It is, therefore, of particular importance that functional fluids be improved so that the corrosion of mechanical members and fluid degradation can be inhibited and controlled.

It has now been found that corrosion of metal mechanical members in contact with functional fluids comprising a major amount of a phosphoroamidate can be inhibited and controlled by the incorporation into said functional fluid of a unique combination of a nitrogen-containing antioxidant and a nitrogen-containing heterocyclic compound selected from (A)--(l) a compound represented by the structure wherein each R is selected from the group consisting of hydrogen, alkyl, amino, substituted amino, hydroxyl and cyano amino, R and R are each selected from the group consisting of hydrogen, amino, substituted amino, alkyl, substituted alkyl, cycloalkyl, aryl and substituted aryl and R and R together can form a cyclic or a substituted cyclic ring, said cyclic and substituted cyclic rings being selected from the group consisting of a carbonand nitrogen-containing heterocyclic ring having from 4 to 10 atoms optionally interrupted by from 1 to 4 nitrogen atoms, and a carbocyclic ring containing from 4 to 10 carbon atoms, a, b and c are each whole numbers having a value of to 1, each X is carbon or nitrogen provided that when each X is nitrogen a, b and c, respectively, have a value of 0 and provided that at least one X is nitrogen, and (2) mixtures thereof;

(B)( 1) A compound represented by the structure wnerein each R is selected from the group consisting of hydrogen, alkyl, amino, substituted amino, hydroxyl and cyano amino, R and R are each selected from the group consisting of hydrogen, amino, substituted amino, alkyl, substituted alkyl, cycloalkyl, aryl and substituted aryl and R and R together can form a cyclic or a substituted cyclic ring, said cyclic and substituted cyclic rings being selected from the group consisting of a heterocyclic ring having from 4 to atoms optionally interrupted by from 1 to 4 nitrogen atoms and a carbocyclic ring containing from 4 to 10 carbon atoms, c, d, e and f are each whole numbers having a vlue of 0 to 1, each X is nitrogen or carbon provided that when X is nitrogen, c, d, e and 1 have a value of 0 and provided that there is present within the compound (a) at least two nitrogen atoms represented by X or (b) at least one nitrogen atom represented by X and a group represented by X -R wherein X is carbon and R is selected from the group consisting of NH monoalkylamino, dialkylamino and cyanoamino, and (2) mixtures thereof:

(C)(1) A compound represented by the structure Rs-N-Xa-(Ra);

wherein R is selected from the group consisting of hydrogen, alkyl, amino, substituted amino, hydroxyl and cyano amino, R and R are each selected from the group consisting of hydrogen, amino, substituted amino, alkyl, substituted alkyl, cycloalkyl, aryl and substituted aryl and R and R together can form a cyclic or a substituted cyclic ring, said cyclic and substituted cyclic rings being selected from the group consisting of a heterocyclic ring having from 4 to 10 atoms optionally interrupted by from 1 to 4 nitrogen atoms, and a carbocyclic ring containing from 4 to 10 carbon atoms, g and h are each whole numbers having a value of 0 to 1, X is nitrogen or carbon provided that when X is nitrogen, g and h have a value of 0, and (2) mixtures thereof; and

(D) Mixtures of any combination of (A), (B) and (C).

This invention encompasses functional fluids comprising a major amount of a phosphoroamidate and a minor amount of an additive composition comprising a mixture of a nitrogen-containing antioxidant together with a nitrogen-containing heterocyclic compound as represented by and Thus the improved functional fluid compositions of the present invention preferably comprise from 60 to about 99.9 percent by weight of a phosphoroamidate base fluid and from 0.001 to percent by weight of a mixture of a nitrogen-containing antioxidant and a nitrogen-containing heterocyclic compound represented by (A), (B), (C) and (D). It is even more preferred that said mixture of the nitrogen-containing heterocyclic compound and the nitrogen-containing antioxidant be present in the composition in amounts of from about 0.1 to about 5 weight percent.

The improved functional fluid compositions of this invention also include those containing from 60 to 99.9 percent by weight of the phosphoroamidate and from 0.001 to 20 percent by weight of the mixture of the nitrogen containing heterocyclic and nitrogen-containing antioxidant together with a small amount, i.e. from 0.5 to 10 percent by weight of phosphoric acid esters, diesters, polyester or complex esters or mixtures thereof.

The phosphoroamidate functional fluid compositions of this invention can be compounded in any manner known to those skilled in the art for the incorporation of additives into a base stock as, for example, by adding the additive composition to the phosphoroamidate base stock with stirring until a homogeneous fluid composition is obtained.

The ratio of the nitrogen-containing antioxidant to the nitrogen-containing heterocyclic compound represented by (A), (B), (C) and (D) in the additive compositions can vary over a wide range and is generally from about 200 to 1 to about 1 to 100, preferably from about 20 to 1 to about 1 to 10. The concentration of an additive composition which is added to a functional fluid as set out above can vary over a wide range and is adjusted in terms of the particular system and the base stock which is utilized in the system. Since the introduction of any foreign element into a functional fluid can alter the properties of the functional fluid, it is generally preferred to incorporate that amount of the additive composition which is sufiicient to inhibit and control corrosion damage. Thus, the concentrations of the nitrogen-containing antioxidant and the heterocyclic compound are adjusted for the particular base stock to which they are added and in addition each additive is adjusted with respect to the concentration of the other additive, such that the total concentration of the two additives is that concentration which is suflicient to inhibit and control corrosion damage. It has been found that in general for the phosphoroamidate functional fluids the concentration of the additive composition which can be utilized within the scope of this invention can vary from about 0.001 weight percent to about 20 weight percent of the total composition preferably from about 0.1 percent to about 5 percent.

Typical examples of nitrogen-containing antioxidants which can be utilized within the scope of this invention are the naphthylamines such as phenyl-a-naphthylamine, phenyl-Bmaphthylamine, butyl-u-naphthylamine, tolyl naphthylamine, etc.; the carbazoles such as N-methyl carbazole, N-ethyl carbazole, 3-hydroxy carbazole, N,ndecyl carbazole, N,B-dimethyla.minoethyl carbazole; the diphenylamines such as diphenylamine, ditolylamine, phenyl tolylamine, 4,4-diamino-diphenylamine, p-(p-toluene sulfonylarnido) diphenylamine, di-p-methoxy-diphenylamine, octylated diphenylamine, p,p-dioctyldiphenylamine, heptylated diphenylamine, N-nitroso diphenylamine, 4-cyclohexylamino diphenylamine, 4'-tertamyl-2,4 diaminodiphenylamine, dipyridylamines such as 2,2'-dipyridylamine, the condensation product of diisobutylene and diphenylamine, etc.; the aminophenols such as N-butylaminophenol, N-methyl-N-amylaminophenol, N-isooctyl p aminophenol, etc.; aminodiphenyl alkaues such as aminodiphenyl methanes, 4,4-diamino diphenyl methane, etc.; aminodiphenyl ethers; aminodiphenyl thioethers; the aryl-substituted alkylenediamines such as 1,2-di-o-toluidoethane, 1,2-dianilinoethane, 1,2- dianilinopropane, etc.; the aminobiphenyls such as S-hydroxy-2-aminobiphenyl, etc; the reaction products of an aldehyde or ketone with an amine such as the reaction product of acetone and phenyl-B-naphthylamine, the reaction product of acetone and diphenylamine, the reaction product of butyraldehyde and aniline, the reaction product of acetaldehyde and aniline, disalidylal ethylenediamine, disalicylal propylenediamine, aldol-ot-naphthylamine; me reaction product of a complex diarylamine and a ketone or aldehyde; the morpholines such as N-(phydroxyphenyl) morpholine, etc.; the amidines such as N,N-bis-(hydroxyphenyl) acetamidine, etc.; the dithiocarbamates such as nickel dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc dioctyldithiocarbamate, zinc diisopropyldithiocarbamate, zinc methylethyldithiocarbamate, etc.; the acridans such as 9,9-dimethylacridan, the guanidine salts of dipyrocatechol borate such as di-o-tolylguanidine salt of dipyrocatechol borate, etc.; the mercaptobenzothiazoles such as zinc mercaptobenzothiazolate, nickel mercaptobenzothiazolate; the phenathiazines such as phenathiazine, 3,7dibutylphenathiazine, 3- n-dodecoxyphenathiazine, 6,7-dioctylphenathiazine, 3-Octylphenathiazine; cyclohexylamines such as dicyclohexylamine, and mixtures thereof.

Typical examples of compounds represented by (A) are imidazoles; imidazolines; indazoles such as 4-amino indazole, S-amino indazole, 6-amino indazole, 7-amino indazole, 4-hydroxy indazole, S-hydroxy indazole, 6-hydroxy indazole, 7-hydroxy indazole; pyrazoles; triazoles such as 1,2,4-triazole, 5-amino-l,2,4-triazole, 3,5-diamino-1,2,4-triazole; indoles such as S-amino indole, S-hydroxy indole, 5,7 diamino 1,2,6,8-tetraazaindolizine, 2,2 octamethylene-di-Z-imidazoline, 5-amino-4-carbamyl-3-pyrazole acetic acid, 7-amino-s-triazolo-(l,5-a)pyrimidin-5-(4H)-one, 4 methyl 1H pyrazole-(3,4-b)-pyridine-3,6-diol and 6- hydroxy indazole.

Typical examples of nitrogen-containing heterocyclic compounds represented by (B) are pyrimidines, such as 4,5-diamino pyrimidine, 4,6-dihydroxy pyrimidine, 4-amino pyrimadole-(4,5-d)-pyrimidine, 4-amino pyrazolo-(3,4-

d)-pyrimidine, 4,5-diamino pyrimidine, 7-amino-lv-triazolo-(d)-pyrimidine and the like; pyridines such as 3,4-diamino pyridine; quinolines such as 3,4-diamino quinoline; ptyridines such as 2,4,7-triamino-5-phenyl ptyridines, 4- hydroxy ptyridine, 7-hydroxy ptyridine, 4-amino pyrimido1e-(4,5-d)-pyrimidineand the like; naphthylimides such as 4-amino-1,8-naphthyl.

Typical examples of heterocyclic compounds represented by (C) are triazines such as 3,5,7-triamino-s-triazolo-(4,3- a)-s-triazine; and indolizines such as 5,7-diamino-1,2,6,8- tetraazaindolizine.

Typical examples of phosphorusamidates base stocks which are employed in the composition of this invention are the amides of an acid of phosphorus which are represented by the structure n Ru wherein Y is selected from the group consisting of oxygen, sulfur and l u .N

and Y is selected from the group consisting of oxygen, sulfur and R R R R13, R and R are each selected from the group consisting of alkyl, aryl, cycloalkyl, substituted aryl, substituted alkyl and a monovalent heterocyclic and substituted heterocyclic ring having from 4 to 10 atoms optionally interrupted by from 1 to 4 hetero atoms in the ring and wherein R R R R R and R each can be identical or difierent with respect to any other radical and mixtures thereof.

Typical examples of alkyl radicals represented by the various R groups above are as follows: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-amyl, isoamyl, 2-methylbutyl, 2,2-dimethylpropyl, l-methylbutyl, diethylmethyl, 1,2-dimethylpropyl, tertamyl, n-hexyl, l-methylamyl, l-ethylbutyl, 1,2,2-trimethylpropyl, 3,3 dimethylbutyl, 1,1,2 trimethylpropyl, 2- methylamyl, 1,1-dimethylbutyl, l-ethyl-2methy1propyl, 1,3-dimethylbutyl, isohexyl, 3-methylamyl, 1,2-dimethylbutyl, l-methyl-l-ethylpropyl, Z-ethylbutyl, n-heptyl, 1,1, 2,3-tetramethy1propyl, 1,2-dimethyl-1-ethylpropyl, 1,1,2- trimethylbutyl, l-isopropyl 2 methylpropyl, l-methyl-Z- ethylbutyl, 1,1-diethylpropyl, Z-methylhexyl, 1,1-dimethylamyl, l-isopropylbutyl, 1-ethyl-3-methylbutyl, 1,4-dimethylamyl, isoheptyl, l-methyl-l-ethylbutyl, 1-ethyl-2- methylbutyl, l-methylhexyl, l-propylbutyl, n-octyl, 1- methylheptyl, 1,1-diethyl 2 methylpropyl, 1,1,3,3-tetramethylbutyl, 1,1-diethylbutyl, 1,1-dimethy1hexyl, l-methyl-l-ethylamyl, l-methyl-l-propybutyl, 2-ethylhexyl, 6- methylheptyl (iso-octyl), n-nonyl, l-methyloctyl, l-ethylheptyl, 1,1-dimethylheptyl, l-ethyl-l-propylbutyl, 1,1-diethyl 3 methylbutyl, diisobutylmethyl, 3,5,5-trimethylhexyl, 3,5-dimethylheptyl, n-decyl, l-propylheptyl, 1,1-diethylhexyl, 1,1-dipropylbutyl, 2-isopropyl-5-methylhexyl and C -C alkyl groups.

It is also contemplated within the scope of this invention that the hydrogen in the previously described alkyl radicals can be replaced by halogen, such as chlorine, bromine and fluorine.

Typical examples of aryl and substituted aryl radicals which the various R groups represent are for example, phenyl, cresyl, xylyl, halogenated phenyl, cresyl and xylyl in which the available hydrogen on the aryl or substituted aryl is partially or totally replaced by a halogen, o, mand p-trifluoromethylphenyl, 0-, mand p-2,2,2-trifluoroethylphenyl, o-, mand p-3,3,3-trifluoropropylphenyl and o-, mand p-4,4,4-trifluorobutylphenyl.

The preferred amides of an acid of phosphorus are those wherein Y and Y are selected from oxygen and 1' 1: i u N and -N-- respectively. Typical examples of the amides of an acid of phosphorus, that is, mono-, diand triamides of an acid of phosphorus, hereinafter defined as phosphoro' amidates, are

phenyl-methyl-N,N-dimethyl-phosphoroamidate; phenyl-methyl-N,N-di-n-butylphosphoroamidate; mixtures of phenyl-m-cresyl-N,N-dimethylphosphoroamidate and phenyl-p-cresyl-N,N-dimethylphosphoroamidate; mixtures of m-cresyl-p'cresyl-NN-dimethylphosphoroamidate, di-m-cresy1-N,N-dimethylphosphoroamidate and di-p-cresy1-N,N-dimethylphosphoroamidate; di-m-bromophenyl-N-methyl-N-n-butylphosphoroamidate; di-m-chlorophenyl-N-methyl-N-n-butylphosphoroamidate; di-a,a,a-trifluoro-m-cresyLN-methyl-N-n-butylphosphoroamidate; di-p-bromophenyl-N-methyl-N-n-isoamylphosphoroamidate; di-p-chlorophenyl-N-methyl-N-n-isoamylphosphoroamidate; p-chlorophenyl-m-bromophenyl-N-methyl-N-nisoamylphosphoroamidate; phenyl-N-methyl-N-butyl-N'-methyl-N-butylphosphorodiamidate; phenyl-N,N-di-n-buty1-N,N,-di-n-butylph0sphorodiamidate; phenyl-N,N-dimethyl-N,N'-dimethylphosphorodiamidate; m-chlorophenyl-N-methyl-N-n-butyl-N'-methyl- N'-n-butylphosphorodiamidate; m-bromophenyl-N-methyl-N-n-butyl-N-methyl- N-n-butylphosphorodiamidate; a,a,a-trifluoro'm-cresyl-N-methyl-N-n-butyl- 7 N'-methyl-N'-n-butylphosphorodiamidate; p-chlorophenyl-N-methyl-N-isbuty1-N'-methyl- N'-isoamylphosphorodiamidate; p-bromophenyl-N-methyl-N-isobutyl-N'-methy1- N'-isoamylphosphorodiamidate; N-methyl-N-butyl-N'-methyl-N'-butyl-N"-methyl- N"-butylphosphorotriamidate; N-methyl-N-butyl-N',N"-tetramethylphosphorotriamidate; N-di-n-propyl-N,N"-tetramethylphosphorotriamidate; and N,N'-di-n-propyl- "-dimethylphosphorotriamidate.

The esters of an acid of phosphorus which can be added in minor amounts, i.e. up to percent by the weight, to the improved functional fluids of this invention are phosphate wherein the alkyl groups contain from 1 to 18 carbon atoms examples of which are set forth above and aryl groups containing from 6 to 16 carbon atoms examples of which are set forth above. Typical examples of these esters of an acid of phosphorus, that is, phosphates, are dibutylphenyl phosphate, triphenyl phosphate, tricresyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, trioctyl phosphate and mixtures of the above phosphates, such as mixtures of tributyl phosphate and tricresyl phosphate, and mixtures of isooctyldiphenyl phosphate and 2-ethylhexyldiphenyl phosphate and mixtures of trialkyl phosphates and tricresyl phosphates and the like.

It is also contemplated within the scope of this invention that the phosphoroamidates can be blended with minor amounts, i.e. up to 10 weight percent of ester compounds, such as diand triester compounds, polyester compounds, complex ester compounds and mixtures thereof. Typical examples of diester compounds, that is, diand tricarboxylic acid esters, which are suitable as base stocks are represented by the structure wherein 0, 0', p and p each are whole numbers having the value of 0 to 1 provided that the sum of each of 0-H; and 0' +p' is 1; A is a whole number having a 'value of l to 2; R and R each can be alkyl, cycloalkyl, substituted alkyl, alkenyl, substituted alkenyl, aralkyl, substituted aralkyl, aryl and substituted aryl; and R can be a hydrocarbon radical and a substituted hydrocarbon radical and can be prepared by esterifying dicarboxylic acids such as adipic acid, azelaic acid, suberic acid, sebacic acid, hydroxysuccinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol, hexyl alcohol, 2 ethylhexyl alcohol, dodecyl alcohol, 2,2- dimethyl heptanol, l-methyl cyclohexyl methanol, etc.

Typical examples of alkyl, aryl, substituted alkyl and substituted aryl radicals are given above.

Polyesters which are suitable as base stocks are represented by the structure ing of hydrogen, alkyl, acyloxy and substituted acyloxy and when Z is 2 to 4 m is 1 and R is selected from the group consisting of acyl and substituted acyl and can be prepared by esterifying such polyalcohols as pentaerythritol, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, trimethylolpropane, trimethylolethane and neopentyl glycol with such acids as propionic, butyric, isobutyric, n-valeric, caproic, n-heptylic, caprilic, 2-ethylhexanoic, 2,2-dimethylheptanoic and pelargonic.

Typical examples of complex esters are represented by the structure wherein R and R are each selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl, substituted aryl, cycloalkyl, substituted cycloalkyl and a carbocyclic radical containing from 6 to 10 carbon atoms; R and R are each selected from the group consisting of alkylene, substituted alkylene, alkenylene, substituted alkenylene, phenylene and substituted phenylene; x is a whole number having a value of from about 1 to about 8-0 and mixtures thereof.

The complex esters are obtained by esterifying dicarboxylic acids with a mixture of monohydric alcohols and a glycol to give complex esters. Complex esters which can be employed can be prepared by esterifying a dicarboxylic acid (1 mole) with a glycol (2 moles) and a monocarboxylic acid (2 moles) or with 1 mole each of a glycol, a dicarboxylic acid and a monohydric alcohol or with 2 moles each of a monohydroxy monocarboxylic acid and a monohydric alcohol. Still other complex esters may be prepared by esterifying a glycol (1 mole) with a monohydroxy monocarboxylic acid (2 moles) and a monocarboxylic acid (2 moles).

Other complex esters which are suitable are prepared by polymerizing a dihydroxy compound with a dicarboxylic acid and reacting the terminal hydroxy and acid radical with a mixture of a monocarboxylic acid and a monohydric alcohol. Specific examples of polymers which may be utilized as additives Within the scope of this in vention are polymers prepared by the polymerization of adipic acid and 1,2-propane diol in the presence of minor amounts of short-chain monocarboxylic acids and a monohydric alcohol to give molecular weights of the polymers tlzlhelrleby produced of from about 700 to about 40,000 or 1g er.

The mono, diand polyhydric alcohols, and the monocarboxylic acids employed in the preparation of the complex esters can also contain ether oxygen linkages.

Specific examples of complex esters which are suitable in accordance with the present invention are esters prepared from methylene glycol (1 mole), adipic acid (2 moles) and Z-ethylhexanol (2 moles); esters prepared from tetraethylene glycol dicarboxylic acids (1 mole) and monocarboxylic acids (2 moles) and complex esters prepared from neopentyl glycol (1 mole) dicarboxylic acids (2 moles) and monohydric neo alcohols, e.g., 2,2,4-trimethylpentanol (2 moles).

One of the major bench scale methods used for evaluating the corrosivity of a lubricant or hydraulic fluid is the procedure according to which the fluid to be evaluated is heated at a specified temperature in the presence of certain metals and air and the corrosivity determined by measuring the change in weight of the metals.

Various compositions of this invention were tested according to the procedure of Modified Federal Test Method 791, Method No. 5308. The metal specimens used were steel, copper, cadmium, magnesium and aluminum. The results observed using the above-described procedure are recorded in Table I below. The corrosivity to metals was determined by weighing the metal specimens before and after the test. The Weight difference in milligrams per square centimeter of metal surface exposed to the fluid is reported. A minus sign indicates that the metal specimen had a net weight loss after the test. In Table I the asterisk indicates that the oxidation and corrosion test'as described above was run at a temperature of 260 F. In all other examples, the temperature of the oxidation and corrosion test was at a temperature of 300 F. and the flow rate of dry air at both temperatures was liters per hour. The designation A refers to a diamidate base stock which is N-methyl-N- butyl-N'-rnethyl-N-butylphenylphosphorodiamidate. The

duration of the oxidation and corrosion test was 168 hours.

to inhibiting and controlling corrosion damage. The combination of additives as above described produces a synergistic improvement, which combination of additives is far superior to the effectiveness of the individual additives. This synergism is entirely unexpected since both additives when utilized separately do not significantly inhibit corrosion damage.

Thus, the employment of the improved functional fluids of this invention inhibits and controls corrosion damage to metals. The inhibition and control of corrosion damage prevents corrosion products from contaminating the fluid which contamination product can cause an increased rate TABLE I Ex. Base Cad- Magne- Total No. Nitrogen-containing antioxidant Heterocyelic compound stock Copper rnium sium acid Sludge 1 1% p.p-diootyl dlphenylamine, 1% N-phenyl-m- None A -29. 70 --4.44 0. 39 14.0 Slight.

naphthylamine. 2 None 0.1% 3,6-d1amino-1,2,4-triazole- A -20. 56 36. 12 -14.95 24.8 Heavy. 3 1% p,p-dioctyl diphenylamlne, 1% N-phenylwto A 0. 16 -01! 0. 01 3.10 None.

naphthylaxnine. 4*.-." None 0.1% b-amino lndazole A --7. 43 2. 53 -0. 30 5 1% pig-(11231253 1 diphenylamine, 1% N-DhQHYl-a- 0.05% 5-amlno indazole A 2. 16 -0. 17 0.17 Slight.

nap y no. 6 .-do 0.1% 4,5-diamino pyrimidene A 0. 30 -0. 60 -0.06 17.0 Do. 7.-- ..do. 0.1% 7-amino indazole A 1.33 -2. O.47 14.0 Do. 8 2% p,p'- dioctyl diphenylamine None A -30. 13 4. 21 3. 77 21. 9 Heavy. 9-- do 0.1% 3,5-diamino-1,2,4-triazole A 2. 19 -0. 37 0. 39 7.2 Slight. 10.- do 0.10% 5-amino indazole A -0.48 0 32 +0. 22 5.0 None.

The same test procedure set forth above was employed with phenyl-di l azacyclopentyl phosphorodiarnidate (base stock B) and phenyl-di(N-methyl-N-n-octyl) phosphorodiarnidate (base stock C) using copper, cadmium, iron and magnesium test specimens. The temperature of the oxidation and corrosion test in all instances was 300 F. The results of these tests are given in Table II.

of oxidation of the fluid. The metal salts can act as pro oxidants thereby increasing fluid damage which manifests itself in numerous Ways, among which are viscosity change, increase acid number, formation of insoluble materials, increased reactivity and discoloration. In a fluid system the particular properties of a fluid have to be maintained in order to continue useful operation of the par- TABLE II Example Base Cad- Magnumber Nitrogen-containing antioxidant Heteroeycllc compound stock Copper rmum neslum Iron 11 None None B 0. 19 -0. 51 12-- do 0.1% 5am.ino indaaole" B -0. 08 0. 47 13.- 1% N-phenyl-a-naphthylamine. None B -0. 13 0. 95 14-- 2.0% N-phenylw-naphthrrlamine. 0.15% S-amlno indazol B -0. 02 0. 36 15-- None.-- None--- C -6. 06 2. 57 16. do 0.1% 2,6diamino pyridine C -1. 2. 63 17.- 2% p,p-dioctyl dipheny1amine. None C -4. 74 0. 07 18-- 0..-- 0.1% 2,6diamino pyr1dme C 0. 52 0. 01

The data in the previous examples demonstrate the significant inhibitions of corrosion damage obtained by the improved compositions of this invention. The physical properties and the performance characteristics of the phosphoroamidate base stock such as lubricity, fire resistance, and viscosity were essentially unafiected, an important consideration since a base stock is selected for a given systern because of its physical properties and characteristics and deviations from these properties and characteristics can bring about inferior fluid performance.

In particular Table I demonstrates that the nitrogencontaining antioxidants when incorporated into a phosphoroamidate base stock as a single component do not inhibit and control corrosion damage. This is well illustrated by Examples Nos. 1, 2,. 4 and 8 in which the copper weight loss was extremely high. With respect to the heterocyclic compound, the copper corrosion remains extremely high and at a level which causes damage to mechanical members in contact with the fluid and in addition fluid degradation. The negative sign indicates that copper has been removed from the metal surface thereby producing corrosion products which remain in the actual system to which the base stock is incorporated. Thus, the high amount of copper loss as reflected by the individual examplesutilizing a nitrogen-containing antioxidant and a nitrogen-containing heterocyclic compound demonstrates that mechanical members in contact with the fluid would no longer have the required geometry and close tolerances which are necessary for the proper operation of a particular system. The combination of the two additives, namely, a nitrogen-containing antioxidant and a heterocyclic compound, give outstanding results with respect ticular system in which the fluids are employed. Thus, changes in viscosity can be produced by fluid degradation whereby polymeric products with high molecular weights are produced in the system. Such high molecular Weight products often become insoluble in the particular base stock which results in the precipitation or sludging of the insoluble material. Such precipitation and sludging plugs filters and deposits on moving parts which have to be lubricated by the fluid thereby causing inadequate lubrication. Increased chemical reactivity is observed on fluid degradation as well as a buildup of the acid number of the fluid. Such increased chemical reactivity and high acid number allows the particular system which incorporates the fluid to be chemically attacked by the fluid thereby causing pitting, wear and alterations of the close tolerances of the mechanical members of said fluid. Thus, premature overhaul of mechanical parts is a direct consequence of fluid degradation. Thus, it is of particular importance that corrosion damage of mechanical members in contact with fluid be inhibited and controlled in order to prevent damage to mechanical members and in addition fluid degradation which can be a direct consequence of contamination of a fluid with corrosion products.

As a result of the excellent inhibition and control of damage utilizing the functional fluid compositions of this invention, improved hydraulic pressure devices can be prepared in accordance with this invention which comprise in combination a fluid chamber and an actuating fluid composition in said chamber, said fluid comprising a mixture of one or more of the base stocks hereinbefore described and a minor amount, suflicient to inhibit and control corrosion damage, of the additive composition of this invention. In such a system, the parts which are so lubricated include the frictional surfaces of the source of power, namely the pump, valves, operating pistons and cylinders, fluid motors, and in some cases, for machine tools, the ways, tablets and slides. The hydraulic system may be of either the constant-volume or the variable-volume type of system.

The pumps may be of various types, including centrifugal pumps, jet pumps, turbine vane, liquid piston gas compressors, piston-type pump, more particularly the variable-stroke piston pump, the variable-discharge or variable displacement piston pump, radial-piston pump, axial-piston pump, in which a pivoted cylinder block is adjusted at various angles with the piston assembly, for example, the Vicker Axial-Piston Pump, or in which the mechanism which drives the pistons is set at an angle adjustable with the cylinder block; gear-type pump, which may be spur, helical or herringbone gears, variations of internal gears, or a screw pump; or vane pumps. The valves may be stop valves, reversing valves, pilot valves, throttling valves, sequence valves, relief valves, servo valves, non-return valves, poppet valves or unloading valves. Fluid motors are usually constantor variable-discharge piston pumps caused to rotate by the pressure of the hydraulic fluid of the system with the power supplied by the pump power source. Such a hydraulic motor may be used in connection with a variable-discharge pump to form a variable-speed transmission. It is, therefore, especially important that the frictional parts of the fluid system which are lubricating by the functional fluid be protected from damage. Thus, damage brings about seizure of frictional parts, excessive wear and premature replacement of parts.

The fluid compositions of this invention when utilized as a functional fluid can also contain dyes, pour point depressants, metal deactivator, acid scavengers, antioxidants, defoamers in concentration suflicient to impart antifoam properties, such as from about to about 100 parts per million, viscosity index improvers such as polyalkylarcrylates, polyalkylmethacrylates, polycyclic polymers, polyurethanes, polyalkylene oxides, polyalkylene polymers, polyphenylene oxides, polyesters, lubricity agents and the like.

It is also contemplated within the scope of this invention that the base stocks as aforedescribed can be utilized singly or as a fluid composition containing two or more base stocks in varying proportions. The base stocks can also contain other fluids which include in addition to the functional fluids described above fluids derived from coal products and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing the alkylene oxide in the presence of water or alcohols, e.g., ethyl alcohol, alkyl benzenes (e.g., monoalkyl benzene such as dodecyl benzene, tetradecyl benzene, etc.), and dialkyl benzenes (e.g., n-nonyl 2-ethylhexylbenzene); polyphenyls (e.g., biphenyls and terphenyls), halogenated benzene, halogenated lower alkylbenzene, halogenated biphenyl, monohalogenated diphenyl ethers, polyphenyl ethers such as a mixture of S-ring polyph'enyl ethers, polyphenyl thioethers, mixed polyphenyl ethers-thioethers, phenoxybiphenyls, phenylmercaptobiphenyls, mixed phenoxy phenylmercaptobiph'enyls, trialkyl phosphine oxides, diarylalkyl phosphonates, trialkyl phosphonates, aryldialkyl phosphonates, triaryl phosphonates and mixtures thereof.

While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims:

What is claimed is:

1. A composition consisting essentially of 12 (A) from 60 to about 99.9 percent by weight of a phosphoroamidate represented by the formula Rn Ru and mixtures thereof wherein Y is oxygen, Y is oxygen or an group, R10, R11, R12, R and R are each individually a C alkyl group, a C aryl group, or a C cycloalkyl group, and (B) from 0.001 to 20 percent by weight of a mixture (1) a mixture of p,p'-dioctyl diphenylamine and N-phenylra-naphthylamine, and (2) S-aminoindazole, and wherein the ratio of (1) and (2) is from 200 to l to 1 to 100. 2. A composition consisting essentially of (A) from 60 to about 99.9 percent by weight of a phosphoroamidate represented by the formula and mixtures thereof wherein Y is oxygen, Y is oxygen or an group, R R R R and R are each individually a C alkyl group, a C aryl group, or a C cycloalkyl group, and (B) from 0.001 to 20 percent by weight of a mixture (1) a mixture of p,p'-dioctyl diphenylamine and N- phenyl-a-naphthylamine, and (2) 7-aminoindazole, and wherein the ratio of (1) and (2) is from 200 to 1 to 1 100. 3. A composition consisting essentially of (A) from 60 to about 99.9 percent by weight of a phosphoroamidate represented by the formula (References on following page) 13 References Cited UNITED STATES PATENTS Peterli et al. 252-401 X Ostrowski 252-390 X Sullivan 252-78 X Blair et al. 252-390 X Blair et a1. 252-390 X Critchley et al. 252-78 Bachman et a1. 252-390 X Szmuszkovicz 252-390 X Blake et a1. 252-78 X Blake et a1 252-78 X 1 4 FOREIGN PATENTS 824,114 11/1959 Great Britain.

OTHER REFERENCES Fire-Resistant Hydraulic Fluid for Submarines, Blake et al., pp. i, 5, 8, 10, 11, 12, 13, Monsanto, 1964.

LEON D. ROSDOL, Primary Examiner H. A. PITLICK, Assistant Examiner US. Cl. X.R. 

